More than one in 20 adults in the UK has a clinically confirmed food allergy, according to a detailed study commissioned by the Food Standards Agency.

The Patterns and Prevalence of Adult Food Allergy report also found that around 36% of people have a self-reported adverse reaction to food.

For UK adults, peanuts and tree nuts like hazelnuts, walnuts and almonds, are most likely to cause an allergic reaction, the analysis found.

But many individuals also had allergies to fresh fruits such as kiwi or apple and these were associated with being allergic to birch pollen.

By contrast allergies to foods like milk, fish, shrimp and mussels are uncommon in adults, the report carried out by the Universities of Manchester and Southampton said.

The analysis updates figures collected more than 30 years ago which found while 20% of the population reported experiencing some sort of food intolerance, only 1.4% had confirmed allergic reactions.

It had been assumed this had become more common because of reported increases in food allergies in children but it had not been studied systematically, the report said.

Overall, it was estimated that 6% of the UK adult population has a clinically confirmed IgE-mediated food allergy with a spectrum of severity of reaction from mild (like oral itching) to anaphylaxis. It equates to 2.4 million people, they added.

Many of the individuals studied were found to have food allergies that were caused by several different foods. Only around half reported having had a food allergy that was formally diagnosed by a doctor.

In addition, around 7% of the population had other types of adverse reactions to food not caused by IgE, such as irritable bowel syndrome and conditions like coeliac disease.

The findings were based on two longitudinal birth cohort studies done in the Isle of Wight and South Manchester, as well as a community survey done for the FSA report in Greater Manchester that included a wide demographic of people.

In the cohort studies it was found that young adults who had developed food allergies as children retained them as they grew up.

But seven out of ten of those in the community study reported that their food allergies developed in adulthood, suggesting the burden of allergies increases in adulthood, the report concluded.

Exposure to environmental allergens, such as birch and related tree pollens, and their relationship with food should be looked at further, the researchers said.

There is also a need to undertake clinical confirmation of non-IgE-mediated adverse reactions in the community survey participants to further assess the burden of other types of adverse food reaction in the UK, they recommended.

Professor Robin May, chief scientific advisor at the Food Standards Agency, said the report was significant in helping identify how food allergies evolve between childhood and adulthood, as well as providing vital insights into links between certain types of foods and the persistence of allergies into adulthood.

‘Through this research, we can see patterns such as the emergence of plant-based allergies affecting more people into adulthood which is important for us to consider as we’ve seen the food system move towards plant-based diets and alternative proteins.’

This article first appeared on our sister publication Pulse.